1. Field of the Invention
This invention relates generally to artificial respiration systems and more particularly to control valves used in the implementation of such systems.
2. Description of the Prior Art
While presently available respiratory systems can furnish a volume of air to a patient's lungs, it is sometimes necessary to predetermine control parameters used to regulate the flow and pressure of breathing gas furnished. It has been found necessary in the operation of such expiratory apparatus to maintain an artificial residual pressure in the lungs under some conditions. This residual pressure may be called positive end expiratory pressure, and the parameter itself is so often used as to rate the acronym PEEP. Thus it is sometimes found necessary to hold a patient's lung pressure constant at the end of an expiratory cycle and through the start of an inspiratory cycle to this predetermined reference pressure, PEEP. Moreover, it is found in practice that the magnitude of the required PEEP may vary somewhat from inspiratory/expiratory cycle to cycle. Some disadvantages of the prior art respiratory systems include the lack of facility of variation of the PEEP after having it set at a particular average value. Thus a patient requiring a particular average value of PEEP over one inspiratory/expiratory cycle and having that value set up operating personnel is limited to that value until a new value is set up by operating personnel.
The basic types of prior art ventilators and respiratory devices are well-known. Many types have been developed and have been in clinical use for many years. Most of these prior art devices have met special needs as presented by specific problems and have thus served narrow purposes. Some of these prior art devices have been described in the following listed patents that were brought to the attention of the applicant through a novelty search conducted in the United States Patent and Trademark Office:
1. Ventilator and Method -- U.S. Pat. No. 3,974,828 -- Forrest M. Bird PA0 2. Volume-Rate Respirator System and Method -- U.S. Pat. No. 3,905,362 -- Theodore B. Eyrick et al PA0 3. Ventilator -- U.S. Pat. No. 3,669,108 -- Leif J. Sundblom et al PA0 4. Therapeutic Intermittent Positive Pressure Respirator -- U.S. Pat. No. 3,434,471 -- Max D. Liston PA0 5. Internally Actuated Combined Oxygen Pressure Regulator and Oxygen-Air Dilution Valves for Respiratory Apparatus -- U.S. Pat. No. 3,386,458 -- Lee S. Wasserman et al PA0 6. Respiratory Apparatus -- U.S. Pat. No. 3,339,545 -- Geoffrey B. Burchell PA0 7. Lung Ventilating Equipment -- U.S. Pat. No. 3,307,542 -- Christian B. Andreasen PA0 8. Intermittent Positive Pressure Breathing Apparatus -- U.S. Pat. No. 3,319,627 -- Fred N. Windsor PA0 9. Resuscitation Apparatus -- U.S. Pat. No. 3,229,689 -- Laurence Christman PA0 10. Lung Ventilators and Timing Devices Therefor -- U.S. Pat. No. 2,880,719 Christian B. Andreasen PA0 11. Resuscitator -- U.S. Pat. No. Re. 23,845 -- Henry Seeler PA0 12. Resuscitator -- U.S. Pat. No. Re. 23,496 -- Henry Seeler PA0 13. Resuscitation Apparatus -- U.S. Pat. No. 2,453,475 -- Cornelius A. Tobias PA0 14. Resuscitator Insufflator Aspirator -- U.S. Pat. No. 2,408,136 -- LeRoy G. Fox PA0 15. Respiration Apparatus -- U.S. Pat. No. 2,121,311 -- Emil E. W. Anderson PA0 16. Resuscitation and Artificial Respiration Apparatus -- U.S. Pat. No. 1,848,232 -- Robert B. Swope et al.
Many of these prior art systems and devices have had defects which have made them inappropriate and sometimes dangerous. Attention is drawn to the fact that none of these prior art devices attempts to regulate a positive end expiratory pressure on a cycle-to-cycle basis, so as to better serve the needs of a patient.
It would thus be a great advantage to the art to provide a system in which a PEEP is adjusted on a cycle-to-cycle basis so as to better serve a patient's cycle-to-cycle needs. It would be a concurrent advantage to provide such a system in a relatively inexpensive and uncomplicated form. A further desirable advantage would be to provide a means whereby existing artificial respiratory systems can be modified to afford adjustment of positive end expiratory pressures in the manner of the contemplation of the invention, in an economical and uncomplicated manner.